1. Field of the Invention
The present invention generally relates to an apparatus useful for measuring the flow of an abrasive fluid. The present invention comprises an apparatus and method of constructing the same particularly useful in the measurement of petroleum liquids flowing from a well head and contaminated with sand or other abrasive materials.
2. Description of the Background
The need for accurate, reliable and durable rotary metering devices for measuring the flow of fluids is well established. Those associated with the oil and gas industry are well aware that it is critical to continuously and accurately measure the flow of petroleum liquids from remote well sites. The devices used for these measurements must be accurate, reliable and durable. Further, because sand and other abrasive materials are often suspended within the produced fluids, these metering devices are prone to failure. The continuous and accurate operability of these devices is critical to the correct measurement of well production. Failure can prove exceedingly expensive in both inaccurate production totals and lost production time. Therefore, accurate, reliable and durable metering devices are a necessity.
The most widely used metering devices employ rotary flow mechanisms based on those disclosed by R. S. Smith in U.S. Pats. Nos. 2,207,182 and 2,263,145, the disclosures of which are incorporated herein by reference. Flowmeters based on these disclosures have been widely adopted throughout the oil and gas industry. The rotor and housing of these meters are typically manufactured from cast iron. Because it was desirable to have lightweight blade mechanisms with these meters, aluminum blades have typically been employed. However, these meters are prone to failure in oil fields producing fluids having high levels of sand or other abrasive materials. Sand and other abrasive materials carried by the well fluids have caused rapid deterioration of these meters resulting in inaccurate production totals and lost production. A particularly troublesome failure point is the rapid deterioration of the fit of the metering blades and the slots in the rotor through which the blades move. The tolerance at this interface is rather small and is particularly subject to rapid erosion when metering fluids containing high levels of sand or other abrasive materials. The presence of sand or other abrasive materials within the well fluids increases the rate at which this gap erodes, thus shortening the useful life of the meter. In fields producing particularly abrasive well fluids, these meters often provide satisfactory operation for only a few months before needing repair or replacement. This rapid deterioration results in inaccurate production totals, lost production and the necessity that the meter be repaired or replaced. These meters are typically repaired by replacing the rotor and/or blades with newly manufactured parts or by installing an entirely new meter. Accordingly, frequent repair or replacement is both time consuming and expensive. However, the more significant economic loss often results from the inaccurate metering of the production fluids and from the loss of production during the repair of the meter.
Accordingly, there has been a long felt but unfulfilled need within the industry for an accurate, reliable and durable metering device, particularly for a long-lasting device useful for metering production fluids containing sand or other abrasive materials.